3.15.0b2, openSUSE/Factory, i586: failing test: test_c_stack_unwind (specifically test_manual_unwind_finds_expected_frames)

[mcepl]

Bug report

Bug description:

As a followup to #151040 I am creating this separate ticket for i586. The traceback is exactly the same:

[ 3208s]   test_manual_unwind_finds_expected_frames (test.test_c_stack_unwind.ManualStackUnwindTests.test_manual_unwind_finds_expected_frames) (env={'PYTHON_JIT': '0'}) ... FAIL
[ 3208s] 
[ 3208s] ======================================================================
[ 3208s] FAIL: test_manual_unwind_finds_expected_frames (test.test_c_stack_unwind.ManualStackUnwindTests.test_manual_unwind_finds_expected_frames) (env={'PYTHON_JIT': '0'})
[ 3208s] ----------------------------------------------------------------------
[ 3208s] Traceback (most recent call last):
[ 3208s]   File "/home/abuild/rpmbuild/BUILD/python315-3.15.0_b2-build/Python-3.15.0b2/Lib/test/test_c_stack_unwind.py", line 285, in test_manual_unwind_finds_expected_frames
[ 3208s]     self.assertGreaterEqual(
[ 3208s]     ~~~~~~~~~~~~~~~~~~~~~~~^
[ 3208s]         python_frames,
[ 3208s]         ^^^^^^^^^^^^^^
[ 3208s]         STACK_DEPTH,
[ 3208s]         ^^^^^^^^^^^^
[ 3208s]         f"expected to find Python frames on {self.machine} with env {env}",
[ 3208s]         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[ 3208s]     )
[ 3208s]     ^
[ 3208s] AssertionError: 1 not greater than or equal to 10 : expected to find Python frames on i686 with env {'PYTHON_JIT': '0'}
[ 3208s] 
[ 3208s] ----------------------------------------------------------------------
[ 3208s] Ran 1 test in 0.276s
[ 3208s] 
[ 3208s] FAILED (failures=1)

Build log shows all used packages and steps required to be taken. The repository with the package source is https://src.opensuse.org/python-interpreters/python315

@vstinner on the other ticket commented:

That's a different architecture. If you care, you should open a separated issue for i586. You pass explicitly -fomit-frame-pointer which goes against PEP 831 (approved in Python 3.15).

Yes, we have -fomit-frame-pointer specifically for i586 architecture.

CPython versions tested on:

3.15

Operating systems tested on:

Linux

[vstinner]

The test checks:

    if "no-omit-frame-pointer" in cflags:
        # For example, configure adds -fno-omit-frame-pointer by default on
        # supported GCC-compatible builds.
        return True
    if "omit-frame-pointer" in cflags:
        return False

It checks for -fno-omit-frame-pointer first, even if -fomit-frame-pointer is defined after. Instead, we should check for flags in order and remembers the last option. See for example:

def python_is_optimized():
    """Find if Python was built with optimizations."""
    cflags = sysconfig.get_config_var('PY_CFLAGS') or ''
    final_opt = ""
    for opt in cflags.split():
        if opt.startswith('-O'):
            final_opt = opt
    if sysconfig.get_config_var("CC") == "gcc":
        non_opts = ('', '-O0', '-Og')
    else:
        non_opts = ('', '-O0')
    return final_opt not in non_opts

[vstinner]

Yes, we have -fomit-frame-pointer specifically for i586 architecture.

You don't want to implement PEP 831? Is there a reason to not implement it?